Project description:Hox genes are required for the development of the intestinal caecum, a major organ of species eating plants. We have analysed the transcriptional regulation of Hoxd genes in caecal buds and show that they are controlled by a series of enhancers located in a gene desert telomeric to the HoxD cluster. The start site of two neighboring and opposite long non-coding RNAs, Hotdog and Twin of Hotdog, specifically transcribed in the caecum, contacts the expressed Hoxd genes in the framework of a topological domain, a large domain of interactions, which ensures a robust transcription of these genes during caecum budding. We show that hedgehogs have kept this regulatory potential despite the absence of caecum, suggesting that these enhancers are used in other developmental situations. In this context, we discuss some striking similarities between the caecum and the limb buds, suggesting the implementation of a common budding tool-kit. Transcriptional activity at the HoxD locus in developing caeca at E13.5 Transcriptional activity at the HoxD locus in developing caeca at E13.5
Project description:Despite the importance of Hox genes in patterning the mouse embryo, few target genes of the Hox transcription factors have been identified. To search for HoxD targets we contrasted gene expression profiles in the presence and absence of the HoxD genes in two tissues where these genes are important in embryonic patterning-the genital bud and the distal domain of the limb. The Del9 mutant, in which all nine HoxD genes are absent, shows perturbed digit and genital morphogenesis. Therefore we used Affymetrix GeneChip arrays to compare gene expression in forelimb autopods and genital buds from wild type and homozygous Del9 E12.5 embryos.
Project description:The combinatorial expression of the Hox genes along the body axes, referred to as the HOX code, is a major determinant of cell fate and plays a prevailing role in generating the animal body plan. In developing limb buds, the paralogous group 13 genes of the HoxA and HoxD clusters are essential for patterning the distal-most limb structures, the digits. Inactivation of HOXA13 and HOXD13 transcription factors (HOX13) leads to complete digit agenesis in mice, but how HOX13 regulate transcriptional outcomes and confer identity to the distal-most limb cells has remained elusive. Here we performed genome-wide profiling of HOX13 by chromatin immunoprecipitation and analyzed the transcriptome and chromatin state of wild type early and late-distal limb buds, as well as Hoxa13-/-;Hoxd13-/- compound mutant limb buds. Our results show that inactivation of HOX13 impairs the activation and repression of putative cis-regulatory modules specific to the late-distal limb cells. Loss of HOX13 also disrupts the specific, spatial patterning of gene expression along the proximal-distal axis of the developing limb buds. These results show that proper termination of the early limb transcriptional program and activation of the late-distal limb program are coordinated by the dual action of HOX13 on cis-regulatory modules.
Project description:During limb development, Hoxd genes are transcribed in two waves: Early on, when the arm and forearm are specified and subsequently, when digits form. While the latter phase is controlled by enhancers centromeric to the HoxD cluster, we show here that the early phase requires enhancers located in the opposite telomeric gene desert. The transition between the two types of regulations involves a functional switch between two distinct topological domains, as reflected by a subset of genes mapping centrally into the cluster, which initially interact with the telomeric domain and subsequently shift to establish new contacts on the opposite side. This transition between two regulatory landscapes generates an intermediate area of low Hox dose developing into the wrist, the transition between our arms and our hands. This intriguing correspondence between genomic and morphological boundaries illustrates the mechanism underlying collinear Hox gene regulation in our developing appendages. Circular Chromosome Conformation Capture (4C seq) at the HoxD locus in developing proximal and distal limbs at E9.5 and E12.5
Project description:Hox genes are required for the development of the intestinal caecum, a major organ of species eating plants. We have analysed the transcriptional regulation of Hoxd genes in caecal buds and show that they are controlled by a series of enhancers located in a gene desert telomeric to the HoxD cluster. The start site of two neighboring and opposite long non-coding RNAs, Hotdog and Twin of Hotdog, specifically transcribed in the caecum, contacts the expressed Hoxd genes in the framework of a topological domain, a large domain of interactions, which ensures a robust transcription of these genes during caecum budding. We show that hedgehogs have kept this regulatory potential despite the absence of caecum, suggesting that these enhancers are used in other developmental situations. In this context, we discuss some striking similarities between the caecum and the limb buds, suggesting the implementation of a common budding tool-kit. Transcriptional activity at the HoxD locus in the hedgehog developing gut at E13.5, Differential gene expression analysis along the hedgehog developing gut
Project description:Hox genes are required for the development of the intestinal caecum, a major organ of species eating plants. We have analysed the transcriptional regulation of Hoxd genes in caecal buds and show that they are controlled by a series of enhancers located in a gene desert telomeric to the HoxD cluster. The start site of two neighboring and opposite long non-coding RNAs, Hotdog and Twin of Hotdog, specifically transcribed in the caecum, contacts the expressed Hoxd genes in the framework of a topological domain, a large domain of interactions, which ensures a robust transcription of these genes during caecum budding. We show that hedgehogs have kept this regulatory potential despite the absence of caecum, suggesting that these enhancers are used in other developmental situations. In this context, we discuss some striking similarities between the caecum and the limb buds, suggesting the implementation of a common budding tool-kit. Transcriptional activity at the HoxD locus in the murine developing gut at E13, Differential gene expression analysis along the murine developing gut
Project description:Hox genes are required for the development of the intestinal caecum, a major organ of species eating plants. We have analysed the transcriptional regulation of Hoxd genes in caecal buds and show that they are controlled by a series of enhancers located in a gene desert telomeric to the HoxD cluster. The start site of two neighboring and opposite long non-coding RNAs, Hotdog and Twin of Hotdog, specifically transcribed in the caecum, contacts the expressed Hoxd genes in the framework of a topological domain, a large domain of interactions, which ensures a robust transcription of these genes during caecum budding. We show that hedgehogs have kept this regulatory potential despite the absence of caecum, suggesting that these enhancers are used in other developmental situations. In this context, we discuss some striking similarities between the caecum and the limb buds, suggesting the implementation of a common budding tool-kit. Chromosome Conformation Capture (4C seq) at the HoxD locus in developing caeca at E13.5
Project description:The combinatorial expression of the Hox genes along the body axes, referred to as the HOX code, is a major determinant of cell fate and plays a prevailing role in generating the animal body plan. In developing limb buds, the paralogous group 13 genes of the HoxA and HoxD clusters are essential for patterning the distal-most limb structures, the digits. Inactivation of HOXA13 and HOXD13 transcription factors (HOX13) leads to complete digit agenesis in mice, but how HOX13 regulate transcriptional outcomes and confer identity to the distal-most limb cells has remained elusive. Here we performed genome-wide profiling of HOX13 by chromatin immunoprecipitation and analyzed the transcriptome and chromatin state of wild type early and late-distal limb buds, as well as Hoxa13-/-;Hoxd13-/- compound mutant limb buds. Our results show that inactivation of HOX13 impairs the activation and repression of putative cis-regulatory modules specific to the late-distal limb cells. Loss of HOX13 also disrupts the specific, spatial patterning of gene expression along the proximal-distal axis of the developing limb buds. These results show that proper termination of the early limb transcriptional program and activation of the late-distal limb program are coordinated by the dual action of HOX13 on cis-regulatory modules.
Project description:Anterior-posterior differences in H3K27me3 and Ring1B enrichment over the 5 prime Hoxd genes in E10.5 murine distal forelimbs. Chromatin immunoprecipitation (ChIP) of H3K27me3 together with Ring1B and by ChIP-on-chip analysis demonstrated that over the 5 prime HoxD locus H3K27me3 enrichment is decreased and Ring1B enrichment is sparse in limb cells derived from the distal posterior forelimb bud of E10.5 mouse embryos. Array design includes 2 biological replicates for H3K27me3 in the cell lines and Ring1B in the limb tissue, and 2 biological replicates and 2 dye swap replicates for H3K27me3 in the limb tissue.
Project description:The mammalian HoxD cluster is positioned at the boundary between two topologically associating domains (TADs), each of them matching a distinct, enhancer-rich regulatory landscape. During limb development, the telomeric TAD controls the early phase of Hoxd gene transcription in future forearm cells, whereas the centromeric TAD subsequently regulates transcription of more posterior Hoxd genes in presumptive digit cells. The TAD boundary is essential as it prevents the terminal Hoxd13 gene to respond to potent forearm enhancers, thereby allowing the formation of proper proximal limb structures. Here we apply chromosome conformation capture onto embryonic proximal and distal limb bud cells micro-dissected from a set of nested deletions involving part- or all- of this boundary region to try to understand the nature and function of this CTCF- and cohesin-rich DNA region. We document a progressive release of the boundary effect, allowing for inter-TAD contacts to be established, which were favoured by the functional status of the newly accessed enhancers. However, the boundary was highly resilient and only a 400kb large deletion including the whole gene cluster was eventually able to merge the two neighbouring TADs into a single structure. We propose that the whole HoxD cluster is a dynamic transcriptional boundary, showing slight variations depending on both the transcriptional status and the ontogenetic context